Well, regarding the Sikh man, it's not the burden of any 'different' individual to conform to avoid abuse. Gay people shouldn't have to act straight, women shouldn't have to dress cautiously, and people shouldn't have to (try to) modify any racial or ethnic characteristics to satisfy a bigoted or violently inclined mainstream.
Removing the turban isn't an easy choice. It has consequences in the community, and consequences for someone's sense of identity. And what to do with the hair -- cut it, just to go out late that occasional night? Then it wouldn't sit right under the turban afterwards ... (I know some Sikhs quite well).
As for the conference, I think that discrimination on the basis of a chosen appearance is significant and might be related and of interest to some of those at the conference. However, it is very different to discrimination on the basis of something permanent, and something culturally and historically informed. Discrimination against those of African heritage has a long, varied and pretty disgusting history, unlike the kind of discrimination a fake-tan addict might have faced. It would have impacted the culture and social experience of people from birth.
So while it might be an interesting discussion, it is unreasonable to equate all forms of discrimination, and it is also unreasonable of a society to demand conformity on the rationale that non-conformity inspires racism or violence.
Does that help?